So the PS1 version of a missing X68000 Sonic fangame has Sonic recoloured red, and Techokami had found the original blue palette still lying around in the executable. So, by using a hex editor to overwrite the red palette with the blue one using the addresses Techo had posted, I have restored Sonic's original colour from the X68000 version.

Ever wonder why Sonic CD had its own jump and skid sounds? The game uses SMPS Z80, a sound driver that's run on the Mega Drive's coprocessor, the Z80. The Z80 is limited in what it can access: it has 0x2000 bytes of RAM, and an 0x8000-byte window into the cartridge. Problem: Sonic CD isn't on a cartridge.

Because of this, the devs had to squeeze every non-PCM sound effect into Z80 RAM... the same RAM that was already being used by the sound driver itself.

To make room, the sound driver was stripped-down, removing the ability to play music, and also for sounds to use the PSG channels. The Mega Drive has two sound chips, one for FM (a synthesiser), and one for PSG (square wave).

So guess which sound effects just happened to use PSG?

And that's why the jump and skid sounds are so different: they were remade in FM.

So how did I get the original sounds back? Well, I didn't feel like adding PSG support back to Sonic CD's driver, so I did the next most logical thing: I ported Sonic & Knuckles's driver to Sonic CD.

Yeah, as it happens, S&K actually uses SMPS Z80 as well. In fact, it uses a later, improved version (S&K uses "Type 2", while SCD uses "Type 1"). While S&K's driver was also stripped-down, it still has PSG support. All I had to do was take out all the code I didn't need, put SCD's sounds in it, add the one or two features SCD's driver has that S&K's doesn't, and paste it in a Sonic CD ISO.

...That was way easier said than done. Trying to make room for all the sounds was an absolute nightmare. At one point I figured out the time travel screen was exploiting a bug in the driver, so the sound wouldn't be cut off right when the screen goes white. Ironically, to "fix" the game, I had to add that bug back in.

All that just so I can hear Sonic CD without the FM jump sound :|

Anyway, since I don't want to upload a 700MB file, I'll just show you how to hex edit your own ISO:

Open your ISO or BIN or whatever in a hex editor, and find the following pattern of bytes: F3 F3 ED 56 18 1F

Thanks to MotorRoach for the extra Tails sprites. It was also his idea, so blame him.
Also, thanks to Clownacy for the Sonic 2 Clone Driver, just so I could use vladikcomper's Mega PCM driver in Sonic 2 easily

Thanks to MotorRoach for the extra Tails sprites. It was also his idea, so blame him. />/>/>/>/>
Also, thanks to Clownacy for the Sonic 2 Clone Driver, just so I could use vladikcomper's Mega PCM driver in Sonic 2 easily